The invention relates to a motor vehicle including a metal component provided on a front side, a rear side and/or a lateral side, in particular a bumper and at least one sensor unit including a capacitively operating sensor and an associated control device for collision detection.
Modern motor vehicles include different restraint means such as an airbag or seat belt tensioner which serve the safety of occupants. In case of a crash these restraint means are controlled via corresponding control devices, wherein the control is not carried out in a static manner but as the case may be, also in dependence on the collision or respectively the severity of the collision. As a consequence, a collision detection device is provided in modern vehicles which allows detecting data which can serve as basis for calculating the severity of a collision. Usually acceleration sensors situated in the front of the vehicle are used for this purpose, however a capacitively operating collision sensor which changes its capacitances in dependence on the actually occurring collision can also be used for data acquisition, see JP 20000326808. The data acquisition has to occur very rapidly, for which usually a time period of 20-50 ms is available. The control device which is assigned to the collision detection unit determines from the recorded measuring values items of collision information such as the relative collision speed or the overlap with the collision partner. For this purpose multiple sensors with narrow perimeters of operation are distributed over the vehicle front are provided.
Because the installed sensors have only narrow perimeters of operation, i.e., due to their small size operate within only a relatively small area relative to the entire possible collision surface, the relative collision speed can only be determined roughly which is due to the fact that the own vehicle often only interacts locally, be it on the front side or on the rear side, with different collision partners who in addition may also have different stiffness characteristics (for example a wall into which the own vehicle drives is significantly stiffer than a vehicle which has a crumple zone). In addition, due to the functioning of the sensors within narrow perimeters of operation an estimation of the overlap with the collision partner is hardly possible. Due to the very short decision time until actuation or triggering of the restraint means a recognition of the impacted side is problematic in case of a collision.